U.S. patent application number 13/272082 was filed with the patent office on 2012-05-10 for leadless cardiac pacemaker with anti-unscrewing feature.
Invention is credited to Kenneth J. Carroll, Alexander Khairkhahan, Paul Paspa, Eric Varady.
Application Number | 20120116489 13/272082 |
Document ID | / |
Family ID | 45938687 |
Filed Date | 2012-05-10 |
United States Patent
Application |
20120116489 |
Kind Code |
A1 |
Khairkhahan; Alexander ; et
al. |
May 10, 2012 |
Leadless Cardiac Pacemaker with Anti-Unscrewing Feature
Abstract
A leadless cardiac pacemaker comprises a housing, a plurality of
electrodes coupled to an outer surface of the housing, and a pulse
delivery system hermetically contained within the housing and
electrically coupled to the electrode plurality, the pulse delivery
system configured for sourcing energy internal to the housing,
generating and delivering electrical pulses to the electrode
plurality. The pacemaker further comprises an anti-unscrewing
feature disposed on either a fixation device of the pacemaker or on
the housing itself. The anti-unscrewing feature can be configured
to prevent the fixation device from disengaging the wall of the
heart.
Inventors: |
Khairkhahan; Alexander;
(Palo Alto, CA) ; Varady; Eric; (San Francisco,
CA) ; Carroll; Kenneth J.; (Los Altos, CA) ;
Paspa; Paul; (Los Gatos, CA) |
Family ID: |
45938687 |
Appl. No.: |
13/272082 |
Filed: |
October 12, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61392886 |
Oct 13, 2010 |
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61422618 |
Dec 13, 2010 |
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Current U.S.
Class: |
607/127 |
Current CPC
Class: |
A61N 1/37518 20170801;
A61N 1/0573 20130101; A61N 1/37512 20170801; A61N 1/37205 20130101;
A61N 1/3756 20130101 |
Class at
Publication: |
607/127 |
International
Class: |
A61N 1/05 20060101
A61N001/05 |
Claims
1. A leadless biostimulator, comprising: a housing sized and
configured to be implanted within a heart of a patient; a primary
fixation device attached to the housing and configured to affix the
biostimulator to a wall of the heart; and an anti-unscrewing
feature disposed on the primary fixation device, the
anti-unscrewing feature configured to prevent the primary fixation
device from disengaging the wall of the heart.
2. The leadless biostimulator of claim 1 wherein the primary
fixation device is a fixation helix.
3. The leadless biostimulator of claim 1 wherein the
anti-unscrewing feature is at least one barb.
4. The leadless biostimulator of claim 3 wherein the at least one
barb is pointed generally proximally away from a distal end of the
fixation device.
5. The leadless biostimulator of claim 1 wherein a first torque
required to insert the fixation device into the wall of the heart
is less than a second torque required to remove the fixation device
from the wall of the heart.
6. The leadless biostimulator of claim 1 wherein the
anti-unscrewing feature is at least one rounded feature.
7. The leadless biostimulator of claim 1 wherein the
anti-unscrewing feature is at least one through-hole.
8. The leadless biostimulator of claim 1 wherein the
anti-unscrewing feature is at least one depression.
9. A leadless biostimulator, comprising: a housing sized and
configured to be implanted within a heart of a patient; a primary
fixation helix attached to the housing and configured to affix the
biostimulator to a wall of the heart; and an anti-unscrewing helix
wound in an opposite direction of the primary fixation helix, the
anti-unscrewing helix attached to the housing.
10. The leadless biostimulator of claim 9 wherein the primary
fixation helix is a right-handed helix and the anti-unscrewing
helix is a left-handed helix.
11. The leadless biostimulator of claim 9 wherein the primary
fixation helix is longer than the anti-unscrewing helix.
12. The leadless biostimulator of claim 9 wherein the
anti-unscrewing helix is positioned outside of the primary fixation
helix.
13. The leadless biostimulator of claim 9 wherein the primary
fixation helix is an electrode.
14. The leadless biostimulator of claim 9 wherein the
anti-unscrewing helix is configured to compress against tissue as
the primary fixation helix is affixed to the wall of the heart.
15. The leadless biostimulator of claim 9 wherein the
anti-unscrewing helix is configured to engage the wall of the heart
in the event the biostimulator unscrews from the wall of the
heart.
16. A leadless biostimulator, comprising: a housing sized and
configured to be implanted within a heart of a patient; a primary
fixation device attached to the housing and configured to affix the
biostimulator to a wall of the heart; and an anti-unscrewing
feature disposed on the housing, the anti-unscrewing feature
configured to prevent the primary fixation device from disengaging
the wall of the heart.
17. The leadless biostimulator of claim 16 wherein the primary
fixation device comprises a fixation helix.
18. The leadless biostimulator of claim 16 wherein the
anti-unscrewing feature comprises a plurality of teeth, barbs, or
other sharpened features.
19. The leadless biostimulator of claim 18 wherein the teeth,
barbs, or other sharpened features are disposed on a distal surface
of the housing.
20. The leadless biostimulator of claim 18 wherein the teeth,
barbs, or other sharpened features are disposed on a tapered
surface of the housing.
21. The leadless biostimulator of claim 18 wherein the teeth,
barbs, or other sharpened features are arranged asymmetrically to
provide resistance only in an unscrewing direction of the primary
fixation device.
22. The leadless biostimulator of claim 16 wherein a first torque
required to insert the fixation device into the wall of the heart
is less than a second torque required to remove the fixation device
from the wall of the heart.
23. The leadless biostimulator of claim 16 wherein the
anti-unscrewing feature is a cleat.
24. The leadless biostimulator of claim 23 wherein the cleat is
positioned on the housing beneath the fixation device.
25. The leadless biostimulator of claim 24 wherein the cleat is
directed towards the fixation device and configured to grab heart
tissue between the cleat and the fixation device to resist
unintentional detachment of the fixation device from the wall of
the heart.
26. The leadless biostimulator of claim 16 wherein the
anti-unscrewing feature is at least one through-hole.
27. The leadless biostimulator of claim 16 wherein the
anti-unscrewing feature is at least one depression.
28. A leadless biostimulator, comprising: a housing sized and
configured to be implanted within a heart of a patient; a primary
fixation device attached to the housing and configured to affix the
biostimulator to a wall of the heart; and at least one through-hole
disposed in the housing, the at least one through-hole configured
to promote tissue in-growth into the through-hole to prevent the
primary fixation device from disengaging the wall of the heart.
29. The leadless biostimulator of claim 28 wherein the at least one
through-hole extends horizontally into the housing.
30. The leadless biostimulator of claim 28 wherein the at least one
through-hole extends along a longitudinal axis of the housing.
31. The leadless biostimulator of claim 28 wherein the at least one
through-hole has a diameter of approximately 0.005'' to 0.04''.
32. The leadless biostimulator of claim 28 wherein the at least one
through-hole extends partially across a diameter of the
housing.
33. The leadless biostimulator of claim 28 wherein the at least one
through-hole extends fully across a diameter of the housing.
34. The leadless biostimulator of claim 28 wherein the at least one
through-hole is filled with a bioabsorbable material.
35. A method of preventing unintentional detachment of a leadless
biostimulator from a heart of a patient, comprising: applying
torque to the leadless biostimulator in a first direction to affix
the leadless biostimulator to heart tissue with a primary fixation
device; applying torque to the tissue in a second direction with an
anti-unscrewing device to prevent disengagement of the leadless
biostimulator from tissue.
36. The method of claim 35 wherein the torque in the second
direction is greater than the torque in the first direction.
37. A method of preventing detachment of a leadless biostimulator
from a patient, comprising: implanting the leadless biostimulator
into heart tissue of the patient; preventing the leadless
biostimulator from detaching from the heart tissue with a
bioabsorbable anti-unscrewing feature; and allowing the
bioabsorbable anti-unscrewing feature to be absorbed by the patient
in less than 3 months.
38. The leadless biostimulator of claim 1 wherein the
anti-unscrewing feature is a suture.
39. The leadless biostimulator of claim 38 wherein the suture is
bio-absorbable.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit under 35 U.S.C. 119 of
U.S. Provisional Patent Application No. 61/392,886, filed Oct. 13,
2010, titled "Leadless Cardiac Pacemaker with Anti-Unscrewing
Feature", and U.S. Provisional Patent Application No. 61/422,618,
filed Dec. 13, 2010, titled "Leadless Cardiac Pacemaker with
Anti-Unscrewing Feature", both of which are incorporated herein by
reference in their entirety.
INCORPORATION BY REFERENCE
[0002] All publications, including patents and patent applications,
mentioned in this specification are herein incorporated by
reference in their entirety to the same extent as if each
individual publication was specifically and individually indicated
to be incorporated by reference.
FIELD
[0003] The present disclosure relates to leadless cardiac
pacemakers, and more particularly, to features and methods by which
they are affixed within the heart. More specifically, the present
disclosure relates to features and methods for preventing a
leadless cardiac pacemaker from unscrewing itself out of
tissue.
BACKGROUND
[0004] Cardiac pacing by an artificial pacemaker provides an
electrical stimulation of the heart when its own natural pacemaker
and/or conduction system fails to provide synchronized atrial and
ventricular contractions at rates and intervals sufficient for a
patient's health. Such antibradycardial pacing provides relief from
symptoms and even life support for hundreds of thousands of
patients. Cardiac pacing may also provide electrical overdrive
stimulation to suppress or convert tachyarrhythmias, again
supplying relief from symptoms and preventing or terminating
arrhythmias that could lead to sudden cardiac death.
[0005] Cardiac pacing by currently available or conventional
pacemakers is usually performed by a pulse generator implanted
subcutaneously or sub-muscularly in or near a patient's pectoral
region. Pulse generator parameters are usually interrogated and
modified by a programming device outside the body, via a
loosely-coupled transformer with one inductance within the body and
another outside, or via electromagnetic radiation with one antenna
within the body and another outside. The generator usually connects
to the proximal end of one or more implanted leads, the distal end
of which contains one or more electrodes for positioning adjacent
to the inside or outside wall of a cardiac chamber. The leads have
an insulated electrical conductor or conductors for connecting the
pulse generator to electrodes in the heart. Such electrode leads
typically have lengths of 50 to 70 centimeters.
[0006] Although more than one hundred thousand conventional cardiac
pacing systems are implanted annually, various well-known
difficulties exist, of which a few will be cited. For example, a
pulse generator, when located subcutaneously, presents a bulge in
the skin that patients can find unsightly, unpleasant, or
irritating, and which patients can subconsciously or obsessively
manipulate or "twiddle". Even without persistent manipulation,
subcutaneous pulse generators can exhibit erosion, extrusion,
infection, and disconnection, insulation damage, or conductor
breakage at the wire leads. Although sub-muscular or abdominal
placement can address some concerns, such placement involves a more
difficult surgical procedure for implantation and adjustment, which
can prolong patient recovery.
[0007] A conventional pulse generator, whether pectoral or
abdominal, has an interface for connection to and disconnection
from the electrode leads that carry signals to and from the heart.
Usually at least one male connector molding has at least one
terminal pin at the proximal end of the electrode lead. The male
connector mates with a corresponding female connector molding and
terminal block within the connector molding at the pulse generator.
Usually a setscrew is threaded in at least one terminal block per
electrode lead to secure the connection electrically and
mechanically. One or more O-rings usually are also supplied to help
maintain electrical isolation between the connector moldings. A
setscrew cap or slotted cover is typically included to provide
electrical insulation of the setscrew. This briefly described
complex connection between connectors and leads provides multiple
opportunities for malfunction.
[0008] Other problematic aspects of conventional relate to the
separately implanted pulse generator and the pacing leads. By way
of another example, the pacing leads, in particular, can become a
site of infection and morbidity. Many of the issues associated with
conventional pacemakers are resolved by the development of a
self-contained and self-sustainable pacemaker, or so-called
leadless pacemaker, as described in the related applications cited
above.
[0009] Self-contained or leadless pacemakers or other
biostimulators are typically fixed to an intracardial implant site
by an actively engaging mechanism such as a screw or helical member
that screws into the myocardium.
[0010] The potential of detachment of the leadless biostimulator
from the implant site would represent an immediately serious event,
as for example, a pacemaker lost from the right ventricle can exit
the heart via the pulmonic valve and lodge in the lung.
SUMMARY OF THE DISCLOSURE
[0011] A leadless biostimulator is provided, comprising a housing
sized and configured to be implanted within a heart of a patient, a
primary fixation device attached to the housing and configured to
affix the biostimulator to a wall of the heart, and an
anti-unscrewing feature disposed on the primary fixation device,
the anti-unscrewing feature configured to prevent the primary
fixation device from disengaging the wall of the heart.
[0012] In some embodiments, the primary fixation device is a
fixation helix.
[0013] In other embodiments, the anti-unscrewing feature is at
least one barb. In some embodiments, the at least one barb is
pointed generally proximally away from a distal end of the fixation
device.
[0014] In some embodiments, a first torque required to insert the
fixation device into the wall of the heart is less than a second
torque required to remove the fixation device from the wall of the
heart.
[0015] In some embodiments, the anti-unscrewing feature is at least
one rounded feature. In other embodiments, the anti-unscrewing
feature is at least one through-hole. In additional embodiments,
the anti-unscrewing feature is at least one depression.
[0016] A leadless biostimulator is provided, comprising a housing
sized and configured to be implanted within a heart of a patient, a
primary fixation helix attached to the housing and configured to
affix the biostimulator to a wall of the heart, and an
anti-unscrewing helix wound in an opposite direction of the primary
fixation helix, the anti-unscrewing helix attached to the
housing.
[0017] In some embodiments, the primary fixation helix is a
right-handed helix and the anti-unscrewing helix is a left-handed
helix. In other embodiments, the primary fixation helix is longer
than the anti-unscrewing helix. In additional embodiments, the
anti-unscrewing helix is positioned outside of the primary fixation
helix.
[0018] In some embodiments, the primary fixation helix is an
electrode.
[0019] In other embodiments, the anti-unscrewing helix is
configured to compress against tissue as the primary fixation helix
is affixed to the wall of the heart.
[0020] The leadless biostimulator of claim 9 wherein the
anti-unscrewing helix is configured to engage the wall of the heart
in the event the biostimulator unscrews from the wall of the
heart.
[0021] A leadless biostimulator, comprising: a housing sized and
configured to be implanted within a heart of a patient; a primary
fixation device attached to the housing and configured to affix the
biostimulator to a wall of the heart; and an anti-unscrewing
feature disposed on the housing, the anti-unscrewing feature
configured to prevent the primary fixation device from disengaging
the wall of the heart.
[0022] In some embodiments, the primary fixation device comprises a
fixation helix.
[0023] In some embodiments, the anti-unscrewing feature comprises a
plurality of teeth, barbs, or other sharpened features. In many
embodiments, the teeth, barbs, or other sharpened features are
disposed on a distal surface of the housing. In some embodiments,
the teeth, barbs, or other sharpened features are disposed on a
tapered surface of the housing. In other embodiments, the teeth,
barbs, or other sharpened features are arranged asymmetrically to
provide resistance only in an unscrewing direction of the primary
fixation device.
[0024] In one embodiment, a first torque required to insert the
fixation device into the wall of the heart is less than a second
torque required to remove the fixation device from the wall of the
heart.
[0025] In some embodiments, the anti-unscrewing feature is a cleat.
In one embodiment, the cleat is positioned on the housing beneath
the fixation device. In other embodiments, the cleat is directed
towards the fixation device and configured to grab heart tissue
between the cleat and the fixation device to resist unintentional
detachment of the fixation device from the wall of the heart.
[0026] In some embodiments, the anti-unscrewing feature is at least
one through-hole. In other embodiments, the anti-unscrewing feature
is at least one depression.
[0027] A leadless biostimulator is provided, comprising a housing
sized and configured to be implanted within a heart of a patient, a
primary fixation device attached to the housing and configured to
affix the biostimulator to a wall of the heart, and at least one
through-hole disposed in the housing, the at least one through-hole
configured to promote tissue in-growth into the through-hole to
prevent the primary fixation device from disengaging the wall of
the heart.
[0028] In some embodiments, the at least one through-hole extends
horizontally into the housing. In other embodiments, the at least
one through-hole extends along a longitudinal axis of the housing.
In some embodiments, the at least one through-hole has a diameter
of approximately 0.005'' to 0.04''. In other embodiments, the at
least one through-hole extends partially across a diameter of the
housing. In additional embodiments, the at least one through-hole
extends fully across a diameter of the housing. In some
embodiments, the at least one through-hole is filled with a
bioabsorbable material.
[0029] A method of preventing unintentional detachment of a
leadless biostimulator from a heart of a patient is provided,
comprising applying torque to the leadless biostimulator in a first
direction to affix the leadless biostimulator to heart tissue with
a primary fixation device, applying torque to the tissue in a
second direction with an anti-unscrewing device to prevent
disengagement of the leadless biostimulator from tissue.
[0030] In some embodiments, the torque in the second direction is
greater than the torque in the first direction.
[0031] A method of preventing detachment of a leadless
biostimulator from a patient is provided, comprising implanting the
leadless biostimulator into heart tissue of the patient, preventing
the leadless biostimulator from detaching from the heart tissue
with a bioabsorbable anti-unscrewing feature, and allowing the
bioabsorbable anti-unscrewing feature to be absorbed by the patient
in less than 3 months.
[0032] In some embodiments, the anti-unscrewing feature is a
suture. In additional embodiments, the suture is
bio-absorbable.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The novel features of the invention are set forth with
particularity in the claims that follow. A better understanding of
the features and advantages of the present invention will be
obtained by reference to the following detailed description that
sets forth illustrative embodiments, in which the principles of the
invention are utilized, and the accompanying drawings of which:
[0034] FIG. 1 illustrates one embodiment of a leadless cardiac
pacemaker or biostimulator.
[0035] FIGS. 2a-2f illustrate embodiments of anti-unscrewing
features disposed on a fixation device of a leadless cardiac
pacemaker.
[0036] FIGS. 3a-3c illustrate various embodiments of
anti-unscrewing helixes on a leadless cardiac pacemaker.
[0037] FIGS. 4a-4f illustrate embodiments of anti-unscrewing
features disposed on a housing of a leadless cardiac pacemaker.
[0038] FIGS. 5a-5p illustrate various embodiments of leadless
cardiac pacemakers having tine assemblies and anti-unscrewing
features.
[0039] FIGS. 6a-6e illustrate various embodiments of through-hole
or partial through-holes incorporated into a leadless cardiac
pacemaker.
[0040] FIGS. 7a-7b illustrate embodiments of a leadless cardiac
pacemaker having an anti-unscrewing feature comprising a
suture.
DETAILED DESCRIPTION OF THE INVENTION
[0041] A leadless cardiac pacemaker can communicate by conducted
communication, representing a substantial departure from
conventional pacing systems. For example, an illustrative cardiac
pacing system can perform cardiac pacing that has many of the
advantages of conventional cardiac pacemakers while extending
performance, functionality, and operating characteristics with one
or more of several improvements.
[0042] In some embodiments of a cardiac pacing system, cardiac
pacing is provided without a pulse generator located in the
pectoral region or abdomen, without an electrode-lead separate from
the pulse generator, without a communication coil or antenna, and
without an additional requirement on battery power for transmitted
communication.
[0043] Various embodiments of a system comprising one or more
leadless cardiac pacemakers or biostimulators are described. An
embodiment of a cardiac pacing system configured to attain these
characteristics comprises a leadless cardiac pacemaker that is
substantially enclosed in a hermetic housing suitable for placement
on or attachment to the inside or outside of a cardiac chamber. The
pacemaker can have two or more electrodes located within, on, or
near the housing, for delivering pacing pulses to muscle of the
cardiac chamber and optionally for sensing electrical activity from
the muscle, and for bidirectional communication with at least one
other device within or outside the body. The housing can contain a
primary battery to provide power for pacing, sensing, and
communication, for example bidirectional communication. The housing
can optionally contain circuits for sensing cardiac activity from
the electrodes. The housing contains circuits for receiving
information from at least one other device via the electrodes and
contains circuits for generating pacing pulses for delivery via the
electrodes. The housing can optionally contain circuits for
transmitting information to at least one other device via the
electrodes and can optionally contain circuits for monitoring
device health. The housing contains circuits for controlling these
operations in a predetermined manner.
[0044] In some embodiments, a cardiac pacemaker can be adapted for
implantation into tissue in the human body. In a particular
embodiment, a leadless cardiac pacemaker can be adapted for
implantation adjacent to heart tissue on the inside or outside wall
of a cardiac chamber, using two or more electrodes located on or
within the housing of the pacemaker, for pacing the cardiac chamber
upon receiving a triggering signal from at least one other device
within the body.
[0045] Self-contained or leadless pacemakers or other
biostimulators are typically fixed to an intracardial implant site
by an actively engaging mechanism such as a screw or helical member
that screws into the myocardium. Examples of such leadless
biostimulators are described in the following publications, the
disclosures of which are incorporated by reference: (1) U.S.
application Ser. No. 11/549,599, filed on Oct. 13, 2006, entitled
"Leadless Cardiac Pacemaker System for Usage in Combination with an
Implantable Cardioverter-Defibrillator", and published as
US2007/0088394A1 on Apr. 19, 2007; (2) U.S. application Ser. No.
11/549,581 filed on Oct. 13, 2006, entitled "Leadless Cardiac
Pacemaker", and published as US2007/0088396A1 on Apr. 19, 2007; (3)
U.S. application Ser. No. 11/549,591, filed on Oct. 13, 2006,
entitled "Leadless Cardiac Pacemaker System with Conductive
Communication" and published as US2007/0088397A1 on Apr. 19, 2007;
(4) U.S. application Ser. No. 11/549,596 filed on Oct. 13, 2006,
entitled "Leadless Cardiac Pacemaker Triggered by Conductive
Communication" and published as US2007/0088398A1 on Apr. 19, 2007;
(5) U.S. application Ser. No. 11/549,603 filed on Oct. 13, 2006,
entitled "Rate Responsive Leadless Cardiac Pacemaker" and published
as US2007/0088400A1 on Apr. 19, 2007; (6) U.S. application Ser. No.
11/549,605 filed on Oct. 13, 2006, entitled "Programmer for
Biostimulator System" and published as US2007/0088405A1 on Apr. 19,
2007; (7) U.S. application Ser. No. 11/549,574, filed on Oct. 13,
2006, entitled "Delivery System for Implantable Biostimulator" and
published as US2007/0088418A1 on Apr. 19, 2007; and (8)
International Application No. PCT/US2006/040564, filed on Oct. 13,
2006, entitled "Leadless Cardiac Pacemaker and System" and
published as WO07047681A2 on Apr. 26, 2007.
[0046] FIG. 1 shows a leadless cardiac pacemaker or leadless
biostimulator 100. The biostimulators can include a hermetic
housing 102 with electrodes 104 and 106 disposed thereon. As shown,
electrode 106 can be disposed on or integrated within a fixation
device 105, and the electrode 104 can be disposed on the housing
102. The fixation device 105 can be a fixation helix or other
flexible or rigid structure suitable for attaching the housing to
tissue, such as heart tissue. In other embodiments, the electrode
106 may be independent from the fixation device in various forms
and sizes. The housing can also include an electronics compartment
110 within the housing that contains the electronic components
necessary for operation of the biostimulator. The hermetic housing
can be adapted to be implanted on or in a human heart, and can be
cylindrically shaped, rectangular, spherical, or any other
appropriate shapes, for example.
[0047] The housing can comprise a conductive, biocompatible, inert,
and anodically safe material such as titanium, 316L stainless
steel, or other similar materials. The housing can further comprise
an insulator disposed on the conductive material to separate
electrodes 104 and 106. The insulator can be an insulative coating
on a portion of the housing between the electrodes, and can
comprise materials such as silicone, polyurethane, parylene, or
another biocompatible electrical insulator commonly used for
implantable medical devices. In the embodiment of FIG. 1, a single
insulator 108 is disposed along the portion of the housing between
electrodes 104 and 106. In some embodiments, the housing itself can
comprise an insulator instead of a conductor, such as an alumina
ceramic or other similar materials, and the electrodes can be
disposed upon the housing.
[0048] As shown in FIG. 1, the biostimulator can further include a
header assembly 112 to isolate electrode 104 from electrode 106.
The header assembly 112 can be made from tecothane or another
biocompatible plastic, and can contain a ceramic to metal
feedthrough, a glass to metal feedthrough, or other appropriate
feedthrough insulator as known in the art.
[0049] The electrodes 104 and 106 can comprise pace/sense
electrodes, or return electrodes. A low-polarization coating can be
applied to the electrodes, such as platinum, platinum-iridium,
iridium, iridium-oxide, titanium-nitride, carbon, or other
materials commonly used to reduce polarization effects, for
example. In FIG. 1, electrode 106 can be a pace/sense electrode and
electrode 104 can be a return electrode. The electrode 104 can be a
portion of the conductive housing 102 that does not include an
insulator 108.
[0050] Several techniques and structures can be used for attaching
the housing 102 to the interior or exterior wall of the heart. A
helical fixation device 105, can enable insertion of the device
endocardially or epicardially through a guiding catheter. A
torqueable catheter can be used to rotate the housing and force the
fixation device into heart tissue, thus affixing the fixation
device (and also the electrode 106 in FIG. 1) into contact with
stimulable tissue. Electrode 104 can serve as an indifferent
electrode for sensing and pacing. The fixation device may be coated
partially or in full for electrical insulation, and a
steroid-eluting matrix may be included on or near the device to
minimize fibrotic reaction, as is known in conventional pacing
electrode-leads.
[0051] Various anti-unscrewing features can be included on the
biostimulator to provide a feature that requires that the torque
necessary to unscrew the biostimulator from tissue is greater than
the torque necessary to unscrew the biostimulator without such a
feature. In some embodiments, the torque necessary to unscrew the
biostimulator from tissue is greater than the torque necessary to
either further screw, engage, or re-engage the biostimulator into
tissue. When an anti-unscrewing feature provides this function, the
chances of a biostimulator accidentally unscrewing or disengaging
itself from the tissue is reduced. It should be noted that the
torque necessary to initially insert a biostimulator into tissue is
greater due to the puncturing or piercing of tissue and the
formation of a helical cavity. Thus, in some embodiments, the
anti-unscrewing features need only provide that the torque
necessary to unscrew the biostimulator from tissue be greater than
the torque necessary to unscrew the biostimulator from tissue after
the biostimulator has already been implanted in tissue (i.e., after
the tissue has been pierced).
[0052] Referring now to FIG. 2a, a leadless biostimulator 200
includes an anti-unscrewing feature disposed on a fixation device
and configured to prevent disengagement of the biostimulator from
tissue. The biostimulator 200 can be similar to the biostimulator
100 of FIG. 1, and thus housing 202, fixation device 205, electrode
206, insulator 208, and header assembly 212 can correspond,
respectively, to housing 102, fixation device 105, electrode 106,
insulator 108, and header assembly 112 described above.
[0053] In FIG. 2a, the anti-unscrewing feature can comprise at
least one barb 214 disposed on the fixation device 205. Any number
of barbs can be positioned along the length of the helix. FIG. 2b
shows a close-up version of the barb 214 of FIG. 2a. Referring to
FIG. 2b, when the fixation device is inserted into the tissue at a
direction d, the barbs 214 can be pointed in the opposite direction
to engage the tissue and prevent disengagement of the fixation
device from the tissue. More specifically, the barbs can be pointed
proximally away from a distal end of the fixation device. In
various embodiments, the angles .alpha. and .beta. can be adjusted
depending on the torque requirements of the particular application.
For example, then angles .alpha. and .beta. can be adjusted so the
torque required to unscrew the device from tissue is larger than
the torque required to re-screw or engage into pre-punctured
tissue. In some embodiments, .alpha. can range from 135 to 180
degrees and .beta. can range from 30 to 135 degrees. Additionally,
the size, number, and/or spacing of the barbs on the fixation
device can be increased or decreased to accommodate a desired
torque requirement. In some embodiments, the barbs extend only a
short distance outwards from the fixation device so as to allow the
fixation device to screw into and engage tissue without causing
excess injury or damage to the tissue. For example, the barbs may
extend less than 5 mm or even less than 1 mm outwards from the
fixation device. In the embodiment of FIGS. 2a-2b, the barbs are
shown on both sides of the fixation device, but in other
embodiments the barbs can be disposed on only a single side of the
fixation device. In other embodiments, barbs can be radially offset
to reduce the cross-sectional profile at any given point along the
fixation device.
[0054] Various other embodiments of anti-unscrewing features
disposed on or within the fixation device are illustrated in FIGS.
2c-2e. In FIG. 2c, the anti-unscrewing feature comprises at least
one rounded feature 216 disposed on the fixation device 205. The
rounded feature can engage tissue when the fixation device is
inserted and provide additional resistance to the fixation device
to prevent the fixation device from disengaging from the tissue. In
some embodiments, the rounded features can range in size from
approximately 0.003'' to 0.030'' in diameter.
[0055] Referring to FIG. 2d, the anti-unscrewing feature can
comprise at least one cutout or hole 218 in the fixation device
205. The cutouts 218 are configured and sized to allow for tissue
ingrowth into the fixation device to prevent the fixation device
from disengaging the tissue. In some embodiments, the cutouts 218
extend all the way through the fixation element 205. In other
embodiments, the cutouts can be depressions or indents into the
fixation element. In some embodiments, the size or diameter of the
cutouts can range from approximately 0.001'' to 0.010'' in
diameter.
[0056] Referring now to FIG. 2e, the anti-unscrewing feature can
comprise of powder or beads 220 disposed on the surface of the
fixation device. In some embodiments, the powder or beads can be
sintered onto the fixation device to increase the surface area of
the fixation device and provide additional friction for preventing
the fixation device from disengaging the tissue.
[0057] FIG. 2f illustrates another embodiment where an
anti-unscrewing feature comprising a barb 214 is combined with
scallops 215 (or other cutout features) to promote tissue ingrowth
and provide friction preventing anti-rotation.
[0058] In some embodiments described above, the anti-unscrewing
feature(s) are stamped, cut, welded onto, etched onto, or otherwise
attached to or disposed on the fixation device. In one embodiment,
the fixation device can be wire-wound and the anti-unscrewing
feature(s) can be added onto the fixation device by an additive
process. In another embodiment, the fixation device can be
subtractively cut from a tube and the anti-unscrewing feature(s)
can be formed during the same process.
[0059] FIGS. 3a-3c illustrate additional embodiments of a
anti-unscrewing feature configured to prevent disengagement of a
biostimulator from tissue. In contrast to the embodiments described
above in FIGS. 2a-2e, where the fixation device or fixation helix
itself included an anti-unscrewing feature, the embodiments of
FIGS. 3a-3b include an anti-unscrewing feature separate from the
fixation device. In FIG. 3a, biostimulator 300 can comprise any of
the biostimulators described herein, thus housing 302, fixation
device 305, and header assembly 312 can correspond, respectively,
to housing 102, fixation device 105, and header assembly 112 of
FIG. 1.
[0060] Referring to the top-down view of biostimulator 300 in FIG.
3a, it can be seen that fixation device 305 is wound in the
clockwise direction, so it follows that biostimulator 300 can be
attached to tissue by winding the biostimulator and the fixation
helix into tissue in a clockwise direction. The biostimulator 300
can further include an anti-unscrewing feature comprising an
anti-unscrewing helix 322. In some embodiments, the anti-unscrewing
helix can be positioned outside of the fixation device 305 and
wound in the opposite direction of the fixation device (i.e., wound
counter-clockwise in FIG. 3a). Thus, if the fixation helix is a
right-handed helix then the anti-unscrewing helix is a left-handed
helix, and vice versa. Positioning the anti-unscrewing helix
outside the fixation device causes any tissue irritation associated
with the anti-unscrewing helix to occur away from the fixation
device (and away from the active pacing electrode if it is disposed
on the fixation helix). In other embodiments, however, the
anti-unscrewing helix can be positioned inside the primary fixation
device.
[0061] The anti-unscrewing helix can be a single helix, double
helix, triple helix, etc. In some embodiments, referring to FIG.
3b, the anti-unscrewing feature can comprise a plurality of
anti-unscrewing helixes 324, to provide enhanced stability to the
overall fixation system. In other embodiments, the anti-unscrewing
helix 322 or helixes 324 can include barbs or other anti-unscrewing
features, such as those described above in FIGS. 2a-2e. In this
example, barbs would only be used if the anti-unscrewing helix is
wound in the same direction as the fixation device or helix.
Winding an anti-unscrewing helix in the opposite direction of the
fixation device can prevent a biostimulator from disengaging tissue
because any counter-rotation of the biostimulator would cause the
anti-unscrewing helix or helixes to engage the tissue. In some
embodiments, the anti-unscrewing helix or helixes can also be used
for sensing or for evoked response.
[0062] FIG. 3c shows a side-view of the biostimulator 300 of FIG.
3a. From FIG. 3c, it can be seen that the fixation device 305 is
longer than the anti-unscrewing helix and extends further from a
distal end of the biostimulator than the anti-unscrewing helix 322.
This allows the fixation device to engage tissue first during
insertion without the anti-unscrewing helix extending into the
tissue. Additionally, it can prevent the anti-unscrewing helix from
interfering with mapping or electrical measurements prior to
fixation of the device into tissue. In some embodiments, the
fixation helix can be fully engaged into tissue, and then the
biostimulator can be counter-turned to cause the anti-unscrewing
helix to also engage the tissue. In some embodiments, the
anti-unscrewing helix can compress in the same manner as a spring,
allowing the anti-unscrewing helix to compress against tissue when
the fixation helix is inserted into tissue. In this embodiment, any
scar tissue caused by the anti-unscrewing helix engaging the tissue
will be positioned away from the primary fixation device or
fixation helix. When the fixation helix comprises an electrode, any
scar tissue cased by the anti-unscrewing helix is advantageously
positioned away from the electrode. As such, the anti-unscrewing
helix is not a secondary fixation element, but rather, will only
engage the tissue in the event the biostimulator unscrews or
loosens from tissue. In FIG. 3c, the anti-unscrewing helix is shown
as being approximately 50% the height of the fixation device. In
other embodiments, the anti-unscrewing helix can be any size with
respect to the fixation device, however it is typically 25-50% of
the height of the fixation device.
[0063] FIGS. 4a-4b illustrate additional embodiments of
anti-unscrewing features separate from the fixation device or
helix. For example, in FIG. 4a, a biostimulator comprising a
housing 402, fixation device 405, insulator 408, and header
assembly 412 can further include teeth 426 disposed on the top or
distal-most surface of the header assembly. In some embodiments,
the teeth can be arranged asymmetrically to provide grip and/or
resistance only in an unscrewing direction to the fixation device.
In FIG. 4b, the header assembly 412 can include a tapered surface
428, and the teeth 426 can be disposed along both the top or
distal-most surface and the tapered surface of the header assembly
to increase the anti-unscrewing surface area.
[0064] FIG. 4c illustrates yet another embodiment of a
biostimulator including an anti-unscrewing feature separate from
the fixation device. FIG. 4c is a close-up view of a distal portion
of a biostimulator 400, showing header assembly 412 and fixation
device 405. In this embodiment, an anti-unscrewing feature can
comprise a cleat or wedge 429 positioned on the header assembly in
close proximity to where the fixation device 405 joins the header
assembly. In FIG. 4c, the cleat resembles a triangle or barb, but
other shapes and designs can be used. When the biostimulator is
fully affixed to tissue by the fixation device or fixation helix
405, tissue can become wedged between the fixation device and the
cleat. When the cleat includes a sharp edge directed towards the
fixation device, as shown in FIG. 4c, tissue grabbed by or wedged
between the cleat and the fixation device can cause the
biostimulator to resist unscrewing and accidental detachment from
the tissue. In FIG. 4c, the cleat is shown positioned underneath
the fixation device. However, in other embodiments, the cleat or
cleats can be positioned on the inside and/or outside surface of
the fixation device. All three locations can be used independently
or in combination, for example. FIG. 4f illustrates yet another
embodiment of a biostimulator having cleats or wedges 429
positioned under the fixation device 405.
[0065] In FIGS. 4a-4c, the teeth are shown as pointing straight up
or being perpendicular to the biostimulator. However, in other
embodiments, the teeth can be angled to one side to increase the
ability of the teeth to engage tissue in the event of an unscrewing
of the device. For example, if the biostimulator is engaged in a
clockwise direction into tissue, the teeth may be angled in the
opposite direction on the biostimulator so as to apply additional
force on the tissue in the event that the biostimulator is
accidentally rotated in the counter-clockwise direction. FIG. 4d
illustrates one embodiment of a biostimulator having teeth 426
which apply force in an unscrewing direction opposite the direction
that a fixation device 405 is inserted/engaged into tissue.
[0066] FIG. 4e illustrates another embodiment of a biostimulator
having teeth 427 arranged in a radial direction around the
biostimulator which are configured to apply force in an unscrewing
direction opposite the direction that a fixation device 405 is
inserted/engaged into tissue.
[0067] Referring now to FIGS. 5a-5k, a biostimulator 500 according
to some embodiments can further include an anti-unscrewing feature
comprising a tine or tines 530 extending radially from the
biostimulator. As before, the biostimulator 500 can include any of
the features described herein, including a fixation device 505 and
a header assembly 512, among other features.
[0068] In FIG. 5a, the biostimulator can include two tines 530
disposed on opposite sides of a distal end of the header assembly
512. In some embodiments, the tines can be directed outwards from
the biostimulator, perpendicular to a longitudinal axis of the
biostimulator. The tines can also be attached at any position on
the biostimulator, but typically will be disposed on a distal
portion of the biostimulator on or near the header assembly 512.
The tines can provide a counter-rotation restorative force to
tissue, such as the cardiac wall when the biostimulator is
implanted within the heart. Referring to FIG. 5b, the biostimulator
can include more than two tines 530 to increase the number of
features available to prevent the fixation device from disengaging
tissue. The tines 530 can typically comprise materials such as
silicone or a soft polyurethane or other bioabsorbable polymer.
[0069] In the embodiment of FIG. 5c, teeth 532 can be molded on the
tines 530. In some embodiments, the teeth can be molded all over
the surface of the tines, or alternatively, as shown in FIG. 5c,
the teeth can be disposed only upon a side of the tines that would
engage tissue upon unscrewing of the biostimulator. So in the
example of FIG. 5c, if the biostimulator and fixation device are
rotated in a clockwise direction to engage the tissue, then the
teeth 532 will only engage the tissue to provide counter-rotation
torque if the device is rotated in the counter-clockwise direction,
as shown by arrows CC. In some embodiments, the tines can comprise
a bioabsorbable material.
[0070] Similarly, in FIG. 5d, the tines 530 can be molded with a
spiral shape to provide asymmetrical torque in only one direction.
Using the example above where the biostimulator and fixation device
are rotated in a clockwise direction to engage the tissue, the
spiral shaped tines 530 of FIG. 5d would bend or compress towards
the biostimulator during tissue engagement (e.g., clockwise
rotation), but would engage the tissue and provide counter-rotation
torque to the biostimulator during rotation in the
counter-clockwise direction, as indicated by arrows CC.
[0071] In FIGS. 5a-5d above, the tines are shown extending
outwardly from the biostimulator in a direction perpendicular to a
longitudinal axis of the biostimulator. However, referring now to
FIG. 5e, it can be seen that the tines can also extend both
radially and proximally from the biostimulator. By angling the
tines vertically, they can provide vertical traction to aid in
anti-unscrewing as well as aid the biostimulator's fixation to
tissue. This can be particularly useful in some cardiac situations,
such as when the biostimulator is disposed within a ventricle.
[0072] FIGS. 5f-5h illustrate additional embodiments comprising a
tine or tines 530 providing anti-unscrewing features to the
biostimulator. In FIG. 5f, the tines can fold against the header
assembly 512 during insertion of the biostimulator into the body.
In some embodiments, the tines can be held in place against the
header assembly by an introducer or catheter, for example. When the
biostimulator exits the introducer or catheter, the tines can
spring outward to assume their anti-unscrewing shape (as shown in
FIG. 5a or 5e, for example). The tines can be formed for a shape
memory material, such as Nitinol, to assume a pre-determined
anti-unscrewing shape. In another embodiment, as shown in FIG. 5g,
the tines can fold into cavities 532 disposed within the header
assembly 512. In yet another embodiment, as shown in FIG. 5h, a
dissolvable capsule 534 (e.g., mannitol, sorbitol, etc) can enclose
the fixation device 505 and tines 530 during implantation of the
biostimulator. Once the biostimulator is inserted into the body,
the mannitol capsule will dissolve, allowing the tines to revert to
their anti-unscrewing position.
[0073] Other tine arrangements are shown in FIGS. 5i-5k. In FIG.
5i, the tines 530 can be folded vertically as well as rotationally
around the biostimulator during implantation. In the embodiment of
FIG. 5j, multiple tines at various distances from the fixation
device 505 can extend outwards from the biostimulator. In FIG. 5k,
short and numerous tines 530 can be disposed on the header
assembly. These tines can be shaped and angled to provide
asymmetrical torque, which means they can provide more rotational
friction in one rotational direction (e.g., counter-clockwise) vs.
the other direction (e.g., clockwise).
[0074] In another embodiment, as shown in FIGS. 5l-5m, tines 530
can be molded as a separate tine assembly 538 and assembled onto
the header assembly 512 of the biostimulator via a non-permanent
connection such as a compression or snap fit. In vivo, the tines
would be fully encapsulated in tissue. If the tines were
permanently connected to the biostimulator, this encapsulation
would make extraction of the biostimulator very difficult. But in
this embodiment, during extraction the biostimulator would separate
from the tine assembly 538 and be removed, while the tine assembly
would be permanently left behind or abandoned. For example, during
an extraction procedure, a pull force would be applied to the
biostimulator. Once the pull force exceeds a specified value, the
tine assembly would separate from the biostimulator's header
assembly. The biostimulator would be subsequently removed and only
the encapsulated tine assembly would remain. Therefore, in this
embodiment, a fully endothelialized, encapsulated, and permanently
fixated tine assembly to cardiac tissue is to be encouraged--it
would aid in the clean separation of the biostimulator from the
tine assembly and it would prevent an accidental embolization of
the tine assembly. In this embodiment, the tines may have design
features intended to encourage permanent cardiac fixation, such as
increased surface roughness, through holes, surface
treatments/coatings, etc. In another embodiment, any of the tines
described above can narrow near the biostimulator such that during
extraction of the biostimulator the tine can break off or sever
from the device.
[0075] FIG. 5n illustrates a variation of the embodiment shown in
FIGS. 5l-5m. In FIG. 5n, tine assembly 538 can be held onto the
leadless pacemaker with suture(s) 540. In some embodiments, the
sutures can be bio-absorbable to allow the tines to detach from the
biostimulator once the suture(s) have been absorbed by tissue. FIG.
5o illustrates a leadless cardiac pacemaker or biostimulator
implanted within a chamber of the heart. In this embodiment, the
pacemaker can include the suture attached tine assembly described
in FIG. 5n. FIG. 5p illustrates a separate retrieval catheter
removing the pacemaker of FIG. 5o from the heart after the
suture(s) have been absorbed by the tissue. Attaching the tine
assembly 538 of FIG. 5n with a bio-absorbable material or suture
allows for easier removal of the pacemaker once the suture(s) have
dissolved.
[0076] FIGS. 6a-6e illustrate other embodiments of a biostimulator
having an anti-unscrewing feature for preventing disengagement of
the biostimulator from tissue. In FIG. 6a, a through-hole 636 can
extend horizontally through the header assembly 612 to promote
tissue in-growth into and across the biostimulator. FIG. 6b is a
cross-sectional view of FIG. 6a along line 6b-6b. The relative size
of through-hole 636 with respect to the size of the header assembly
can be seen in FIG. 6b. In some embodiments, the through-holes can
have a diameter of approximately 0.005'' to 0.04''. Although a
single and circular through-hole is illustrated in FIGS. 6a-6b, it
should be understood that any number and shape of through-holes can
be used in the biostimulator, such as square, rectangular,
octagonal, etc. The through-holes can also "neck-down" (i.e., the
through-hole can have a narrower diameter towards the center of the
device than it does on an outside or perimeter of the device.
[0077] Furthermore, the through-holes do not necessarily have to
extend through the entire assembly. Referring to FIG. 6c, the
through-holes 636 can extend partially within the header assembly
612. In the embodiment of FIG. 6d, the through holes extend into
the header assembly in a vertical direction, instead of the
horizontal direction of the through-holes in FIGS. 6a-6c.
[0078] FIGS. 7a-7b illustrate side and top-down views,
respectively, of yet another embodiment of a biostimulator having
an anti-unscrewing feature for preventing disengagement of the
biostimulator from tissue. In FIGS. 7a-7b, the biostimulator can
comprise sutures 742 disposed on the biostimulator and/or on
fixation device 705. In some embodiments, the sutures can be
bio-absorbable. The sutures can be affixed to the biostimulator
and/or fixation device by any methods known in the art, such as by
mechanical interference, adhesives, soldering, etc. In some
embodiments, the sutures can be less than approximately 1-2 mm in
length. In other embodiments, the sutures can be larger. The
sutures can be configured to bio-absorb in tissue after
approximately 30-60 days in some embodiments. In some embodiments,
the sutures can be configured to fold against the biostimulator or
the fixation device as the biostimulator is inserted into tissue,
but the sutures can be configured to expand outwards and engage
tissue if the biostimulator and fixation device is unscrewed. As
shown in FIG. 7b, in some embodiments the sutures can be applied to
point in a direction opposite of the fixation device. Winding the
biostimulator in the opposite direction of the fixation device can
prevent the biostimulator from disengaging tissue because any
counter-rotation of the biostimulator would cause the sutures to
engage the tissue.
[0079] Features such as cavities and through holes that promote
tissue in-growth into and through the biostimulator can increase
fixation of the device to tissue and prevent anti-unscrewing and
disengagement of the biostimulator from tissue. Although many of
the embodiments described herein include features to promote tissue
in-growth, it should be understood that many of the anti-unscrewing
features described herein are configured to prevent unintentional
detachment of the biostimulator from tissue immediately after
implant, but before tissue has had time to grow into the device. In
the embodiment of FIG. 6e, the through-holes 636 are angled with an
orifice on a distal face of the biostimulator.
[0080] The through-holes described herein can be open and free of
any obstructing material, or alternatively, can be filled with a
fast-dissolving substance, such as mannitol, or with a slowly
bioabsorbable material. The advantage of filling the through-holes
or cavities prior to implantation of the biostimulator is that it
eliminates the risk of trapped air embolism and cavities that can
serve as a nidus for bacterial growth.
[0081] The anti-unscrewing features described herein are intended
to prevent a biostimulator from unintentionally unscrewing or
disengaging from tissue. These features are most critical at the
time shortly following implantation of the biostimulator (e.g.,
within 1-3 months of implantation). After 1-3 months
post-implantation, endothelialization will have had sufficient time
to occur such that the biostimulator is fully encapsulated by
tissue. The probability of a fully encapsulated biostimulator
inadvertently unscrewing itself from tissue is assumed to be
relatively low.
[0082] Features to prevent unscrewing may be designed to be most
effective in the short time period post-implant (e.g., within the
first 1-3 months after implantation). These anti-unscrewing
features can therefore be manufactured out of a bio-absorbable
material. Once they are no longer needed to prevent unscrewing of
the biostimulator, they can bioabsorb and disappear. Thus, any of
the anti-unscrewing features described herein, including tines,
barbs, teeth, secondary or anti-unscrewing helixes, and
through-holes may be manufactured out of bioabsorbable materials to
be absorbed by the body after the initial 1-3 month time period
post-implant.
[0083] Various other embodiments of anti-unscrewing features
disposed on or within the fixation device are illustrated in FIGS.
7a-7c. In FIG. 7a, anti-unscrewing feature 740 can be wound around
the surface of fixation device 705. In this embodiment, the
anti-unscrewing feature 740 is configured to prevent disengagement
of the fixation device from tissue. The anti-unscrewing feature 740
can comprise a wire or other similar material that engages the
tissue as the fixation device is inserted into tissue. In some
embodiments, the anti-unscrewing feature can comprise a
bio-absorbable material.
[0084] FIG. 7b illustrates a fixation device 705 comprising
cut-outs or indentations 742 along the length of the fixation
device. As shown in FIG. 7b, the cut-outs 742 comprise
semi-circular cutouts into the fixation device. These cut-outs
allow for tissue ingrowth after the fixation device has been
inserted into tissue. Although not shown in FIG. 7b, the cut-outs
can comprise other shapes, including triangular, square,
rectangular, etc shaped cut-outs.
[0085] FIG. 7c illustrates yet another embodiment of a fixation
device that includes anti-unscrewing features. In the embodiment of
FIG. 7c, fixation device 705 includes through-holes 744 and barbs
746. The through-holes can be disposed along the length of the
fixation device. In the embodiment of FIG. 7c, the through-holes
are disposed along the main surface 748 of the fixation device, and
along the narrow edge surface 750 of the fixation device. The barbs
746 are illustrated as being disposed only along a distal portion
of the fixation device, but in other embodiments, the barbs can be
disposed along any or all parts of the fixation device. In some
embodiments, the barbs can comprise a bio-absorbable material that
dissolves after the fixation device has been inserted into tissue
(e.g., 1-3 months after implantation).
[0086] FIGS. 8a-8c illustrate embodiments of a leadless cardiac
pacemaker in which the electrode 802 is separate from the fixation
device 805. FIGS. 8a and 8b are side and top view, respectively, of
pacemaker 800 having an electrode 802 separate from fixation device
805. In FIG. 8a, the electrode is mounted on flexible arm 852 which
extends outwardly from the body of the pacemaker. As shown in FIG.
8b, the flexible arm can extend radially outwards from the
pacemaker to provide additional resistance against tissue in the
event that the pacemaker begins to unscrew or become dislodged from
tissue. The arm can include additional anti-unscrewing features,
such as through-holes, barbs, teeth, etc to further prevent
anti-unscrewing. In some embodiments, the flexible arm is flexible
in only one direction of rotation (e.g., the direction of rotation
that would allow for the leadless pacemaker to unscrew from
tissue), and is stiff or non-flexible in the other direction of
rotation.
[0087] FIG. 8c shows an alternative embodiment of a pacemaker
having an electrode 802 nestled within fixation device 805. The
pacemaker can be attached to tissue by screwing fixation device 805
into the tissue, which brings electrode 802 into contact with the
tissue. Anti-unscrewing features 854 can be added to prevent the
pacemaker from accidentally dislodging or unscrewing itself from
tissue. The anti-unscrewing features 854 can extend distally from
the body of the pacemaker, as shown, to engage tissue as the
pacemaker is implanted.
[0088] As for additional details pertinent to the present
invention, materials and manufacturing techniques may be employed
as within the level of those with skill in the relevant art. The
same may hold true with respect to method-based aspects of the
invention in terms of additional acts commonly or logically
employed. Also, it is contemplated that any optional feature of the
inventive variations described may be set forth and claimed
independently, or in combination with any one or more of the
features described herein. Likewise, reference to a singular item,
includes the possibility that there are plural of the same items
present. More specifically, as used herein and in the appended
claims, the singular forms "a," "and," "said," and "the" include
plural referents unless the context clearly dictates otherwise. It
is further noted that the claims may be drafted to exclude any
optional element. As such, this statement is intended to serve as
antecedent basis for use of such exclusive terminology as "solely,"
"only" and the like in connection with the recitation of claim
elements, or use of a "negative" limitation. Unless defined
otherwise herein, all technical and scientific terms used herein
have the same meaning as commonly understood by one of ordinary
skill in the art to which this invention belongs. The breadth of
the present invention is not to be limited by the subject
specification, but rather only by the plain meaning of the claim
terms employed.
* * * * *